Vortex states in magnetic nanodisks are essentially affected by surface/interface induced Dzyaloshinskii-Moriya interactions. Within a micromagnetic approach we calculate the equilibrium sizes and shape of the vortices as functions of magnetic field,
the material and geometrical parameters of nanodisks. It was found that the Dzyaloshinskii-Moriya coupling can considerably increase sizes of vortices with right chirality and suppress vortices with opposite chirality. This allows to form a bistable system of homochiral vortices as a basic element for storage applications.
The interplay between intrinsic and surface/interface-induced magnetic anisotropies strongly in- fluences magnetization processes in nanomagnetic systems. We develop a micromagnetic theory to describe the field-driven reorientation in nanomagnets wit
h cubic and uniaxial anisotropies. Spin configurations in competing phases and parameters of accompanying multidomain states are calculated as functions of the applied field and the magnetic anisotropies. The constructed magnetic phase diagrams allow to classify different types of the magnetization reversal and to provide detailed analysis of the switching processes in magnetic nanostructures. The calculated magnetization profiles of isolated domain walls show that the equilibrium parameters of such walls are extremely sensitive to applied magnetic field and values of the competing anisotropies and can vary in a broad range. For nanolayers with perpendicular anisotropy the geometrical parameters of stripe domains have been calculated as functions of a bias field. The results are applied to analyse the magnetization processes as observed in various nanosystems with competing anisotropies, mainly, in diluted magnetic semiconductor films (Ga,Mn)As.
